Electron tube envelope walls of cooling coils welded together



Dec. 13, 1966 s. E. ALLEN, JR 3,292,027

- ELECTRON TUBE ENVELOPE WALLS OF COOLING COILS WELDED TOGETHER Filed Feb. 28, 1964 2 Sheets-Sheet 1 INVENTOR. STANLEY E.ALLEN Jr m w h T N N N v In] :I] o i@ 5 v Q m T n. flwm mmm N 9 2 v QE ATTORNEY Dec. 13, 1966 s ALLEN, JR 3,292,027

ELECTRON TUBE ENVELOPE WALLS OF COOLING COILS WELDED TOGETHER Filed Feb. 28, 1964 2 Sheets-Sheet 3 INVENTOK STANLEY E. ALLEN Jr.

BY Z

ATTORNEY United States Patent f 3,292,027 ELECTRON TUBE ENVELOPE WALLS OF COOLING COILS WELDED TOGETHER Stanley E. Allen, .Ir., Sunnyvale, Calif., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed Feb. 28, 1964, Ser. No. 348,234 4 Claims. (Cl. 313-24) This invention relates generally to electron tube apparatus and more particularly to liquid cooled vacuum envelopes.

In high power or super power electron tube apparatus, large amounts of power must be transferred away from various portions of the tube envelope. For example, in thehigh power beam tube such as a klystron, heat generated in the drift tube sections and in the collector must be transferred. In general, this has been achieved in the past by brazing cooling coils to the drift tube sections and to the collector, or by jacketing these parts so that coolant may flow adjacent thereto. Jacketing is expensive and often, so-called dead spaces develop where the coolant does not circulate. The temperature may build up to such an extent at these portions of the structure as to cause boiling of the coolant and further reduction in heat transfer, and possibly burning of the tube envelope. Another method of cooling has been to braze or secure tubing, often in the form of a coil, to the envelope portions. This requires good conductive contact with the tube portion to be cooled, or again hot spots will develop Where the thermal resistance is high.

It is an object of the present invention to provide an envelope portion which also functions as the cooling assembly.

It is a further object of the present invention to provide a cooled envelope portion suitable for receiving coolant and easy to fabricate in any desired shape.

It is still another object of the present invention to provide an envelope portion which is economical and simple in construction.

It is still a further object of the present invention to provide an envelope portion suitable for receiving coolant which efiiciently conducts heat away from the associated tube envelope.

It is another object of the present invention to provide a cooled envelope portion formed by adjacent convolutions of tubing sealed to one another to form a vacuumtight envelope portion.

The foregoing and other objects of the invention will become more clearly apparent from the following description taken in conjunction with the accompanying drawings.

Referring to the drawing:

FIGURE 1 is a fragmentary side elevational view of an electron tube apparatus incorporating the present invention;

FIGURE 2 is an enlarged view of a drift tube section of the electron tube apparatus of FIGURE 1;

FIGURE 3 is an enlarged view of the portion 33 of FIGURE 2;

FIGURE 4 is a longitudinal foreshortened view, partially in section, of a high power electron tube apparatus incorporating a collector in accordance with the present invention;

FIGURE 5 is an enlarged sectional view of a portion of the collector shown in FIGURE 4; and

FIGURE 6 is an enlarged view of the portion 66 of FIGURE 5.

Generally, the envelope portion in accordance with the present invention is formed of adjacent convolutions of conduit shaped to the desired envelope configuration and sealed to one another to form a vacuum-tight envelope.

3,292,027 Patented Dec. 13, 1966 The envelope can be easily fabricated by winding adjacent convolutions on a form or mandrel and subsequently brlzlazing or welding the adjacent convolutions to one anot er.

Referring now to FIGURE 1, the electron tube comprises a cathode assembly 1 which serves to project a beam of electrons axially down the tube in cooperative relationship with the interaction gaps to be presently described. The operation and construction of a tube of this type is found in Patent 2,971,115. Resonators 2, 3, 4 and 5 are located along the axis of the tube andarranged to cooperate with the electron beam passing therethrough. The collector 6 collects the electron beam. Signal energy to be amplified is supplied to the first resonator 2 via a coaxial transmission line 7, and amplified in successive resonators 3 and 4. The amplified signal is extracted at the resonator 5 and propagated to the load through a wave guide 8.

Referring to FIGURE 2, an enlarged view of the reentrant cavity resonators 3 and 4 and associated drift tube sections is shown. In accordance with the present invention, the drift tube sections and associated envelope portion are formed by a plurality of adjacent convolutions of hollow conduit, such as circular tubing 13. The adjacent convolutions of the tubing are sealed to one another as, for example, by brazing compound 14, and provide a vacuum-tight envelope portion.

Referring more particularly to FIGURE 1, the first convolution of the first drift tube receives the coolant which flows through the various convolutions and to the next drift tube section along an interconnecting conduit 16, etc. The last coil of the last drift tube section is connected by tubing 18 to an outlet connection 19.

The end convolutions of each drift tube section are sealed to cylindrical drift tube members 21, suitably sealed to the adjacent cavities. The members cooperate with one another to form the interaction gaps 22.

Thus, the cooling structure not only serves the function of cooling the drift tube section, but also in itself forms the drift tube section and envelope whereby there is efficient cooling of the drift tube section. A structure of this type may be easily formed by winding adjacent convolutions on a mandrel and then brazing the adjacent convolutions to one another. I

The use of adjacent convolutions to form a cooling structure which is also an envelope portion is illustrated in the collector of the electron device shown in FIG- URES 4 and 5. Referring more particularly to FIGURES 4 and 5, there is shown a high power electron tube apparatus, namely, a klystron incorporating a collector in accordance with the present invention. More particularly, the tube comprises an evacuated envelope formed in part by the novel envelope portion of the present invention which defines the collector. The evacuated envelope can be evacuated to suitable low pressure as, for example, 10 mm. of mercury by an appendage pump 32 such as an ion pump in gas connection with the interior of the envelope through a suitable tabulation 33.

An electron gun assembly 34 is disposed at one end of the tube envelope and serves to form and project a beam of electrons over a predetermined path axially and longitudinally of the envelope 31 in cooperative relation ship with the interaction structure disposed along the envelope. The collector structure 35 is disposed at the other end of the envelope to collect the electron beam.

The collector structure is formed of a plurality of adjacent convolutions of conduit increasing in diameter from the lower end adjacent the last interaction gap to a section of constant diameter (cylindrical) 37 to a section of decreasing diameter 38 to form the collector shown and illustrated. The collector may be formed by winding the adjacent convolutions on three forms, removing the forms, connecting the tubing forming the various convolutions and then brazing the adjacent convolutions together to form the collector.

A plurality of reentrant cavity resonators are disposed along the envelope and form the interaction structure. The inputand output resonators 38 and 39 are arranged along the beam path in axially spaced relationship so that the electromagnetic energy can interact with the beam passing therethrough. Input wave energy to be amplified is applied to the input'resonator 38 via the input loop 10 and coaxial line 11. Amplified output wave energy is extracted in a conventional manner from the output reson ator 39 through the window 40. Axially movable tun ing structures 43 are disposed within the cavity resonators 38 and 39 for tuning the tube over the operating frequency range. 1 A solenoid 44 coaxially surrounds the elongated vacuum envelope 31 and provides an axially directed beam focusing magnetic field as, for example, a field having a strength of lO0 gauss. The magnetic field confines the bearnto a predetermined beam diameter and directsthe same axially along the tube. A hollow cylindrical magnetic shield 15 of soft material surrounds the solenoid for minimizing leakage.

Atthe gun end of the tube 34, the shield 15 abuts an apertured plate 56, of soft metal, forming the top of an iron tank containing an oil bath 57 in which the gun end of the tube, including the solenoid 41, is immersed. The

iron of the tank forms a portion of the magnetic shield.

The oil bath having a dielectric strength greater than air reduces the probability of arc-over across the insulators of the gun structure 34.

In operation, input signals are applied to the input resonators at the coaxial line 11; the signals are amplified in successive resonators and an amplified output signal'is recovered from the tube at the window 40.

A typical tube may utilize a beam voltage in the order of 140 kilovolts and the beam current in the order of 100 amps with an average power in the order of megawatts to produce hundreds of kilowatts of average and tens of magawatts of peak ultrahigh frequency output power. In

such power tubes, with an average beam power being a megawatt or more, the energy of the beam entering the collector must be efficiently dissipated or the collector will burn out;

- In accordance with the present inventiomthe collector structure is formed of the plurality of adjacent convolutions of conduit or tubing, receives the electrons directly, and the heat is rapidly transferred through the walls of the tubing to the coolant passing therethrough.

Thus, it is seen that in both embodiments of the invention, a portion of the vacuum envelope is formed by the cooling structure which is comprised ot-a plurality of adjacent convolutions of a hollow conduit in which the adjacent convolutions are brazed or sealed to one another to form the vacuum envelope and also arranged to pro- 'vide flow of coolant therethrough for cooling. The shape of the envelope portion can be easily controlled by appropriate winding of the adjacent convolutions on a form or mandrel. A structure which is simple in construction, easy to manufacture, inexpensive and highly eflicient is, therefore, provided.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not limiting in sense.

I claim:

1. In an electron tube apparatus including an envelope, an envelope portion comprising a plurality of convolutions of conduit sealed to one another to form a vacuumtight envelope portion and sealed to the adjacent -envelope to define therewith the tube envelope, said convolutions of conduit providing means for circulating a coolant therethrough to cool said portion of the envelope.

2. In an electron tube apparatus of the type in which a beam of electrons is projected along an electromagnetic structure and a collector is disposed to receive said electron beam and form part of the evacuated envelope, said collector comprising a plurality of convolutions of conduit sealed to one another to form a vacuum-tight envelope portion and sealed to the remainder of the tube envelope to complete the same, said convolutions of conduit providing means for circulating a coolant therethrough to cool said collector.

3. In an electron tube apparatus of the type in which an electron beam is projected through a plurality of spaced drift tube sections defining interaction gaps, at least one drift tube section comprising a plurality of convolution of conduit sealed to one another to form a vacuum-tight envelope portion and sealed to said tube envelope to form a portion of the tube envelope, said convolutions of conduit providing means for circulating a coolant therethrough to cool the envelope.

4. In an electron tube apparatus of the type in which an electron beam is projected through a plurality of spaced drift tube sections defining interaction gaps and collected by a collector, said collector comprising a plurality of convolutions of conduit sealed to one another to form a vacuum-tight envelope portion and joined to the adjacent portion of the tube envelope, and at least one of said drift tube sections comprising a plurality of adjacent convolutions of conduit sealed to one another to form a vacuumtight envelope portion and scaled to said tube envelope to form a portion of the same, said convolutions of conduit defining said drift tube and said collector providing means for circulating a coolant therethrough to cool said collector and said drift tube. 

1. IN AN ELECTRON TUBE APPARATUS INCLUDING AN ENVELOPE, AN ENVELOPE PORTION COMPRISING A PLURALITY OF CONVOLUTIONS OF CONDUIT SEALED TO ONE ANOTHER TO FORM A VACUUMTIGHT ENVELOPE PORTION AND SEALED TO THE ADJACENT ENVELOPE TO DEFINE THEREWITH THE TUBE ENVELOPE, SAID CON- 